Showing papers in "Polymers for Advanced Technologies in 2018"
TL;DR: In this article, an integrated composites laboratory at Shandong University of Science and Technology (Shandong 266590) was used for the development of a composites-based computer-aided manufacturing (CAM) system.
Abstract: School of Materials Science and Engineering, North University of China, No. 3 Xueyuan Road, Taiyuan, Shanxi 030051, PR China College of Chemical and Environmental Engineering, Shandong University of Science and Technology, Qingdao, Shandong 266590, China 3 Integrated Composites Laboratory, Department of Chemical and Biomolecular Engineering, University of Tennessee, Knoxville, Tennessee 37996, USA Department of Chemistry, Xavier University of Louisiana, New Orleans, Louisiana 70125, USA Department of Physics and Engineering, Frostburg State University, Frostburg, Maryland 21532, USA
220 citations
TL;DR: In this paper, the authors have shown that the polar crystalline β-phase of polyvinylidene fluoride (PVDF) can be enhanced from 48.2% to 76.1% just by adding ZnO nanorods into the PVDF matrix without any mechanical or electrical treatment.
Abstract: Harvesting energy from the ambient mechanical energy by using flexible piezoelectric nanogenerator is a revolutionary step toward achieving reliable and green energy source. Polyvinylidene fluoride (PVDF), a flexible polymer, can be a potential candidate for the nanogenerator if its piezoelectric property can be enhanced. In the present work, we have shown that the polar crystalline β-phase of PVDF, which is responsible for the piezoelectric property, can be enhanced from 48.2% to 76.1% just by adding ZnO nanorods into the PVDF matrix without any mechanical or electrical treatment. A systematic investigation of PVDF-ZnO nanocomposite films by using X-ray diffractometer, Fourier transform infrared spectroscopy, and polarization-electric field loop measurements supports the enhancement of β-phase in the flexible nanocomposite polymer films. The piezoelectric constant (d33) of the PVDF-ZnO (15 wt%) film is found to be maximum of approximately −1.17 pC/N. Nanogenerators have been fabricated by using these nanocomposite films, and the piezoresponse of PVDF is found to enhance after ZnO loading. A maximum open-circuit voltage ~1.81 V and short-circuit current of 0.57 μA are obtained for 15 wt% ZnO-loaded PVDF nanocomposite film. The maximum instantaneous output power density is obtained as 0.21 μW/cm2 with the load resistance of 7 MΩ, which makes it feasible for the use of energy harvesting that can be integrated to use for driving small-scale electronic devices. This enhanced piezoresponse of the PVDF-ZnO nanocomposite film-based nanogenerators attributed to the enhancement of electroactive β-phase and enhanced d33 value in PVDF with the addition of ZnO nanorods.
111 citations
TL;DR: In this article, a polyurethane network with self-healing capability at mild temperature conditions was successfully prepared in a 1-pot procedure, where disulfide metathesis reformulated the covalent bonds on a longer time scale and non-covalent H-bonding gave rise to a healing efficiency of around 46% in the early healing processing.
Abstract: Tough and transparent polyurethane networks with self-healing capability at mild temperature conditions were successfully prepared in a 1-pot procedure. The self-healing ability of synthesized polyurethane comes from the covalent disulfide metathesis and non-covalent H-bonding. The mechanical testing indicates that disulfide metathesis reforms the covalent bonds on a longer time scale, while H-bonding gives rise to a healing efficiency of around 46% in the early healing processing. The compromise between mechanical performance and healing capability is reached by tailoring the concentration of disulfide. The tensile strength of the sample with 100% self-heal efficiency can get to 5.01 MPa, which can be explained by higher mobility of polymer chain under ambient temperature from creep testing.
107 citations
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TL;DR: In this paper, a novel phosphorus-containing, nitrogen-containing and sulfur-containing reactive flame retardant (BPD) was successfully synthesized by 1-pot reaction and the intrinsic flame-retardant epoxy resins were prepared by blending different content of BPD with diglycidyl ether of bisphenol-A (DGEBA).
Abstract: A novel phosphorus-containing, nitrogen-containing, and sulfur-containing reactive flame retardant (BPD) was successfully synthesized by 1-pot reaction. The intrinsic flame-retardant epoxy resins were prepared by blending different content of BPD with diglycidyl ether of bisphenol-A (DGEBA). Thermal stability, flame-retardant properties, and combustion behaviors of EP/BPD thermosets were investigated by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), limited oxygen index (LOI) measurement, UL94 vertical burning test, and cone calorimeter test. The flame-retardant mechanism of BPD was studied by TGA/infrared spectrometry (TGA-FTIR), pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS), morphology, and chemical component analysis of the char residues. The results demonstrated that EP/BPD thermosets not only exhibited outstanding flame retardancy but also kept high glass transition temperature. EP/BPD-1.0 thermoset achieved LOI value of 39.1% and UL94 V-0 rating. In comparison to pure epoxy thermoset, the average of heat release rate (av-HRR), total heat release (THR), and total smoke release (TSR) of EP/BPD-1.0 thermoset were decreased by 35.8%, 36.5% and 16.5%, respectively. Although the phosphorus content of EP/BPD-0.75 thermoset was lower than that of EP/DOPO thermoset, EP/BPD-0.75 thermoset exhibited better flame retardancy than EP/DOPO thermoset. The significant improvement of flame retardancy of EP/BPD thermosets was ascribed to the blocking effect of phosphorus-rich intumescent char in condensed phase, and the quenching and diluting effects of abundant phosphorus-containing free radicals and nitrogen/sulfur-containing inert gases in gaseous phase. There was flame-retardant synergism between phosphorus, nitrogen, and sulfur of BPD.
67 citations
TL;DR: A composite of acrylonitrile butadiene styrene and MOF-5, a prototypical MOF, which is often used to benchmark H2 uptake capacity of other MOFs, and the ability of the composite to uptake more H2 than the pure polymer.
Abstract: The push to advance efficient, renewable, and clean energy sources has brought with it an effort to generate materials that are capable of storing hydrogen. Metal-organic framework materials (MOFs) have been the focus of many such studies as they are categorized for their large internal surface areas. We have addressed one of the major shortcomings of MOFs (their processibility) by creating and 3D printing a composite of acrylonitrile butadiene styrene (ABS) and MOF-5, a prototypical MOF, which is often used to benchmark H2 uptake capacity of other MOFs. The ABS-MOF-5 composites can be printed at MOF-5 compositions of 10% and below. Other physical and mechanical properties of the polymer (glass transition temperature, stress and strain at the breaking point, and Young's modulus) either remain unchanged or show some degree of hardening due to the interaction between the polymer and the MOF. We do observe some MOF-5 degradation through the blending process, likely due to the ambient humidity through the purification and solvent casting steps. Even with this degradation, the MOF still retains some of its ability to uptake H2, seen in the ability of the composite to uptake more H2 than the pure polymer. The experiments and results described here represent a significant first step toward 3D printing MOF-5-based materials for H2 storage.
TL;DR: In this article, the authors reviewed the research progress of mostly used elastomers, and a circumstantial understanding about the features of ablation and insulation has been validated, especially in the elastomeric heat shielding materials with various reinforcing agents.
Abstract: Catastrophic breakdown that occurs during the flight of supersonic vehicles demands more focused research in the insulation of rocket engines. At present, optimization of polymeric ablatives as viable insulation for solid rocket motor casing has a prominent role in the successful mission of rockets. Among polymers, elastomer serves an imperative part. Comprehensive investigations were disclosed, especially in the elastomeric heat shielding materials with various reinforcing agents. In this paper, research progress of mostly used elastomers is reviewed, and a circumstantial understanding about the features of ablation and insulation has been validated.
TL;DR: In this article, three typical boron compounds, zinc borate (ZB), BPO4, and BORON oxide (B2O3), blended with phosphaphenanthrene compound TAD were incorporated into epoxy resin, respectively.
Abstract: To explore the component synergistic effect of boron/phosphorus compounds in epoxy resin (EP), 3 typical boron compounds, zinc borate (ZB), boron phosphate (BPO4), and boron oxide (B2O3), blended with phosphaphenanthrene compound TAD were incorporated into EP, respectively. All 3 boron/phosphorus compound systems inhibited heat release and increased residue yields and exerted smoke suppression effect. Among 3 boron/phosphorus compound systems, B2O3/TAD system brought best flame-retardant effect to epoxy thermosets in improving the UL94 classification of EP composites and also reducing heat release most efficiently during combustion. B2O3 can interact with epoxy matrix and enhance the charring quantity and quality, resulting in obvious condensed-phase flame-retardant effect. The combination of condensed-phase flame-retardant effect from B2O3 and the gaseous-phase flame-retardant effect from TAD effectively optimized the action distribution between gaseous and condensed phases. Therefore, B2O3/TAD system generated component synergistic flame-retardant effect in epoxy thermosets.